If the machine is in reasonable condition, not too much wear, then I think you will find they are a well made accurate machine. I've never used one but a friend had one for many years and built several locomotives, a Dore Westbury mill and a Quorn on it. Portass built machines for many other distributors and had a reputation for no frills but sound machines.
If it's in reasonable condition, tooled up and suited to the type of work you plan to use it for , I'd rip their arm off, can't see you losing on it even if you decide to change it at a later date. I had a Drummond M of a similar vintage and it was a great lathe that I liked using, still regret selling it as I thought I should upgrade to a newer machine, wrong again!
Dave